In two cases, patients complained of severe pain during the treatment with the NIT so that the application had to be stopped. These teeth (one maxillary and one mandibular molar) were not included in the histological assessment. Macroscopic evaluation of their apices did not show signs of resorption or an widely open apex. In14 of the remaining teeth, some blood was discernible in the adaptor after removing the piston pump.
According to the amount of remaining debris in the respective root section, the roots were allotted to one of the three gradings of remaining debris (D1-D3).The percentages of roots with the respective grading of remaining debris in the apical, middle or coronal part of the roots are presented in Table 1. Statistical analysis proved a significant difference between the various root sections (P < 0.001). In the coronal part, the majority of the roots (55%) were totally clean and free of residual debris (D1).In this root section, however, 33% showed the highest degree of remaining debris (D3).With increasing depth of the canal towards the middle and apical parts of the roots, the percentage of roots with D3 drastically increased, whereas the percentage of completely cleansed canals (D1) decreased.
In the only nonvital tooth, which was the only single rooted tooth as well, residual debris was discernible only in the most apical part of the root canal (Fig. 1). The remaining parts of this root canal were totally free of debris. For the multirooted teeth, no distinct differences were seen amongst the different roots (Fig. 2).This means that in the multirooted teeth the efficacy of cleaning was very similar for the different roots of the same tooth.
The mean values of remaining debris in the respective root sections are illustrated in Fig. 3. It is obvious that the amount of residual debris significantly increased from the coronal to the apical sections of the roots. The statistical analysis revealed significant differences between the three root sections. The P-values of the respective comparisons are delineated in Fig. 3.
Figure 1. Root of a single rooted tooth with some pulpal tissue remnants (arrow) in the most apical part of the root.
Figure 2. Multirooted tooth showing similar amounts of residual pulpal tissue in the two roots.
Table 1. Percentage of roots with remaining debris of gradeD1-D3 in the apical, middle and coronal parts of the roots.
Figure 3. Mean percentage and SEM (standard error of means) of remaining debris in the coronal, middle and apical root sections with the P-values of the statistical comparisons.